Readability checker. Five scores.
Paste your text; get Flesch Reading Ease, Flesch-Kincaid grade, Gunning Fog, SMOG, and Automated Readability Index plus sentence-level warnings. Browser-only; nothing is saved.
Paste any text; get five scores.
Long sentences + hard words.
Readability is engagement, compounded.
Readability scores estimate the US school grade a reader needs to comfortably understand a piece of text. The Flesch Reading Ease score - 0-100, higher is easier - is the most cited; Flesch-Kincaid, Gunning Fog, SMOG, and ARI all output a grade level using slightly different weights on sentence length and syllable density. For most web content, target Flesch Reading Ease of 60-70 and Flesch-Kincaid grade 8 or below. The US average reading level is grade 7-8; writing above grade 10 measurably reduces dwell time and completion across B2B and B2C content alike.
Five scores, five different blind spots. Flesch Reading Ease is the headline number - directly interpretable as "easy / standard / difficult". Flesch-Kincaid grade level is the same formula expressed as a grade, useful when matching content to an audience. Gunning Fog weights complex-word density, so it over-penalizes technical writing where jargon is unavoidable. SMOG (Simple Measure of Gobbledygook) was designed for healthcare documents and is stricter on longer passages. Automated Readability Index uses character count instead of syllables, which is faster to compute but less accurate for multi-syllable variation. Showing all five is the defense against over-indexing on any single number.
Readability does not directly influence Google rankings - there is no published readability signal. It influences engagement metrics (time on page, scroll depth, CTR from SERPs) which compound into rankings over time. Studies from Ahrefs, Backlinko, and Yoast all correlate grade-8-or-below content with 30-60 percent higher dwell time than grade-12 content. For AI search (ChatGPT, Perplexity, Google AIO), the same threshold applies - LLMs cite passages that answer questions cleanly, and cleaner prose extracts better.
The five highest-impact moves for improving a score, in order. One, split any sentence over 25 words - single biggest lever; every comma-separated clause that becomes its own sentence drops grade level. Two, replace multi-syllable corporate fillers with plain alternatives: "utilize" - "use", "commence" - "start", "facilitate" - "help", "individuals" - "people". Three, convert passive voice to active: "The report was written by the team" - "The team wrote the report"; same meaning, simpler reading. Four, break paragraphs over 150 words into 2-3 shorter ones. Five, add subheadings every 200-400 words so readers scan. Moves one and two typically deliver 2-4 grade improvement on their own.
Related tools: Headline analyzer for the H1 above the body text. Keyword density checker for SEO tuning. Meta tag preview for how the content reads in SERPs. Schema markup generator for the structured-data layer.
Seven answers.
What is Flesch Reading Ease and what is a good score?
Flesch Reading Ease is a 0-100 score developed by Rudolf Flesch in 1948. Higher numbers mean easier to read. 90-100 is fifth-grade level. 60-70 is standard US reading level - the target for most web content. 30-50 is college level. 0-30 is graduate / very difficult. The formula: 206.835 - 1.015 * (words/sentences) - 84.6 * (syllables/words). For SaaS and DTC marketing copy, aim for 60-70; for technical docs, 40-50 is fine; for broad consumer content, push to 70+. Yoast's green / orange / red thresholds map directly to this score.
What is the difference between Flesch-Kincaid grade and Gunning Fog?
Both output a US school grade level but use different formulas. Flesch-Kincaid Grade Level weights syllables per word (0.39 * words/sentences + 11.8 * syllables/words - 15.59); it punishes multi-syllable words. Gunning Fog weights complex words (words of 3+ syllables) differently (0.4 * (words/sentences + 100 * complexWords/words)); it punishes density of hard words rather than overall syllable count. Use Flesch-Kincaid as the primary; use Gunning Fog as a sanity check when your content has lots of technical terms. Target grade 8 or below for general web content; grade 10-12 for trade publications; grade 14+ for academic writing.
Why does my content score at grade 14 when I thought it was simple?
Three common causes. One, long sentences - every comma-separated clause pushes grade level up. Split any sentence over 25 words. Two, multi-syllable words - replace utilize with use, commence with start, individuals with people. Three, passive voice - The report was written by the team scores worse than The team wrote the report even though the meaning is identical. The tool flags sentences over 25 words in red; rewriting those three to five sentences usually moves the score 1-2 grades.
What readability level should I target for SEO?
Grade 8 or lower. The average US reading level is grade 7-8 (Literacy in America, NCES 2020). Content that scores higher than grade 10 has lower dwell time, higher bounce rate, and underperforms in ranking - not because Google has a readability algorithm, but because user-engagement signals (time on page, scroll depth, click-through from SERPs) all degrade when readers struggle. For AI search (ChatGPT, Perplexity, Google AIO), the same threshold applies: LLMs cite passages that answer questions clearly, and grade-8 passages answer more clearly than grade-14 ones.
Does readability correlate with SEO rankings?
Not directly. Google has no public readability ranking factor. But readability correlates with downstream ranking factors: dwell time, scroll depth, CTR from SERPs, and now citation-worthiness for AI answers. Studies from Backlinko, Ahrefs, and SE Ranking over 2023-2025 consistently show content at grade 8 or below outperforms higher-grade content on time-on-page by 30-60 percent. The causation is indirect (easier to read = more likely to finish = more likely to convert) but the effect is real. Optimize for reader comprehension; rankings follow.
How do I improve a readability score?
Five moves, in order of impact. One, split any sentence over 25 words - single biggest lever. Two, replace multi-syllable corporate words with plain alternatives (utilize - use, commence - start, facilitate - help). Three, convert passive voice to active (50-70 percent of business writing is unnecessarily passive). Four, break paragraphs over 150 words into 2-3 shorter ones. Five, add subheadings every 200-400 words. The first two moves typically deliver a 2-4 grade improvement; the remaining three polish it.
Does this tool save my text?
No. Every word you paste lives in memory for this browser tab only. Nothing is transmitted to a server, stored in a database, or synced across devices. Close the tab and the text is gone. The Copy scores button puts a summary of the readability scores on your clipboard; the original text stays local.
Readable content converts.
Our growth-strategy and UX engagements include a content audit: readability scoring across pages, prose rewrites for the five highest-traffic URLs, and a style guide that keeps new writing grade-8 without sacrificing voice. Scoped quote in 48 hours.